We received a pre-made (I know, I know….) outdoor wooden playhouse from the father in law. The box claims it’s Chinese Cedar (It doesn’t list a species and I have seen that Chinese Cedar can actually be any number of woods).

Anyways, my real question is in regards to the finish. I thought I would try some oil to protect it from the weather. This is basically my first attempt at finishing a real project. I have read that you can renew and refresh outdoor woods with linseed oil. So I coated the entire thing in Boiled Linseed Oil. I am now reading that BLO promotes mildew. My question is, have I made a mistake? Can I count on the BLO or will it be a guaranteed failure? If so how can I correct it? Can I just coat with Danish Oil on top or something similar? Do I need to somehow remove the BLO?

I have one hatchet handle worth of finishing experience. I have done a ton of reading, but there is so much conflicting advice I don’t know what to believe.

13 replies so far

Nothing wrong with using the BLO. Most oil finishes have a lot of blo in them. You will need to renew it annually and it doesn’t have a lot of UV protection. You might go over everything with an exterior polyurethane that will give you some UV protection and also some abrasion resistance. You can put the poly over the BLO without any problem once the BLO has cured.

Spar Urethane is marketed for outdoor use. My experience with outdoors has been poor as the sunlight will cause it to crack and peel in a short time. Then, you have to sand it all off before recoating. A quality exterior paint or deck stain would be a better option. Olympia Deck Stain has held up reasonably well for me.

Thanks gfadvm. What do you think of my original question though? Does the BLO seem like a BAD idea? I get the feeling it may not be BEST, but my concern is whether it’s actually BAD. Could I put an oil based deck stain on top of the BLO? I actually found some beautiful colored ones at Lowe’s, I believe Olympia. I almost bought that for the roof, but I ended up buying oil based paint instead for the coloration I wanted and the price ($15 vs. $50).

I’m with gfadvm, use Olympic deck stain or thompson’s water seal. I’ve used the Olympic stain on a raised fish pond made with 2×8s and it’s held it’s color for a couple years and have had no problems with the moisture around it.

Since you put BLO on make sure any coating you put on top,is OIL based,not water based.Where you’ll get mildew is if it’s in a wet area that doesn’t get much sun.like under a evergreen tree,etc. if it’s in the sun part of the day you should be fine.look in the deck stain dept.for long lasting coatings.If you have a real paint store like a sherwin-williams or other brand,Not the lowe’s HD,etc.talk to them they know more about paint (they deal with the pros) than a min wage works paint today,lumber next week.

dawg, The location where it’s going to be will get sun from roughly noon-sunset, depending on the time of year. Do you think in that case I can leave the BLO and not worry about mildew? Should I apply some kind of roof sealant or some coating where it contacts the ground?

It seems the prevailing opinion is to add a deck stain on top of the BLO. That’s a bummer, because I was hoping to have this finished this week. I did BLO on both inside and out. Can I get away with just using deck stain on the outside? Will the stain penetrate properly since I applied the BLO or do I need to somehow remove it?

That deck stain is water based. I would worry about putting it over BLO (adherence issues?). You could always roll a coat of Seal Coat shellac over the BLO and then apply the deck stain. Sorry to add another step but at least the shellac will dry almost instantly.

I’d suggest that you may be worrying about nothing. The BLO is an oil and shouldn’t be washed away by water. Mildew grows where it’s dark, damp and low air circulation. BLO may not stop mildew growth on its own, but I don’t see any reason it would promote it unless it just never cures for some reason. If it were me, I leave it as is and keep an eye on it. If you see mildew starting to form, wash the whole thing down and apply an oil based sealer over the BLO. In a year or so, you’ll have to re-oil it anyway so you can decide then whether to go with the BLO again or put something else on. Unless I saw a problem forming before then, I wouldn’t fool with it.